1 & 1/2 cups of buttermilk (I used plain homemade yogurt)
zest and juice of 1 lemon (1 T zest, 2 T juice)
1/3 cup sugar
1 tsp vanilla extract
Stir the sugar with the lemon zest, juice, and vanilla extract. Let it stand 5 minutes. Then stir to dissolve the sugar - gently; this will tke few minutes. Stir in the buttermilk and then chill for at least an hour.
Process in a one-pint ice cream maker. OR freeze in a flat pan and scrape it once every hour for 4 hours to make it slushy.